T lymphocytes mediate immune system function by recognizing membrane antigen on antigen-presenting cells, virus-infected cells, cancer cells, and grafts. Binding of antigen to T lymphocytes either causes the cells to proliferate and secrete various cytokines, which activates an immune response, or causes the T lymphocyte to acquire cytotoxic activity to aid in the immune response.
While essential to the immune response, aberrant T cell responses have been implicated in a number of disorders. For instance, autoimmune diseases such as rheumatoid arthritis and multiple sclerosis are thought to result, in part, from T cells recognizing self antigens as foreign. Conversely, dampened immune/T cell responses may play a role in some malignant cancers.
G-protein-coupled receptors (GPCRs) are of great biological significance, as the malfunction of GPCRs has been implicated in the onset of many diseases, including, but not limited to, Alzheimer's, Parkinson, diabetes, dwarfism, color blindness, retinal pigmentosa and asthma. Also, GPCRs have also been implicated in depression, schizophrenia, sleeplessness, hypertension, anxiety, stress, renal failure and in several cardiovascular, metabolic, neurologic, oncology-related and immune disorders (Horn & Vriend, (1998) J. Mol. Med. 76: 464–468). GPCRs have also been shown to play a role in HIV infection (Feng et al., (1996) Science 272:872–877).
GPCRs are integral membrane proteins characterized by the presence of seven hydrophobic transmembrane domains that together form a bundle of antiparallel alpha (α) helices. The 7 transmembrane regions are designated as TM1, TM2, TM3, TM4, TM5, TM6, and TM7. These proteins range in size from under 400 to over 1000 amino acids (Strosberg, (1991) Eur. J. Biochem. 196:110; Coughlin, (1994) Curr. Opin. Cell Biol. 6:191–197). The amino-terminus of a GPCR is extracellular, is of variable length, and is often glycosylated. The carboxy-terminus is cytoplasmic and generally phosphorylated. Extracellular loops of GPCRs alternate with intracellular loops and link the transmembrane domains. Cysteine disulfide bridges linking the second and third extracellular loops may interact with agonists and antagonists. The most conserved domains of GPCRs are the transmembrane domains and the first two cytoplasmic loops. The transmembrane domains account for structural and functional features of the receptor. In some G-protein coupled receptors, the bundle of α helices forms a ligand-binding pocket formed by several G-protein coupled receptor transmembrane domains.
P2Y10 (GenBank Accession Number AF000545; SEQ ID NOs:1 and 2) is a putative 7-transmembrane GPCR that appears to show lymphoid-restricted expression (Rao et al., (1999) J. Biol. Chem. 274:34245–34252). Indeed, northern blot analysis of RNA showed P2Y10 expression in B and T cells with undetectable levels in macrophages and fibroblasts. In mice, the P2Y10 promoter contains a PU.1/Spi-B binding site required for P2Y10 transcription. Although it is not the present inventors' intention to be bound by any particular theory of operation, because the PU.1 and Spi-B transcription factors have been implicated in B cell receptor signaling in mice (Rao et al., (1999) J. Biol. Chem. 274:34245–34252), the present inventors speculated there is a connection between B cell receptor signaling and P2Y10 in humans. The present inventors further speculated there is a connection between T cell receptor signaling and P2Y10 in humans.
Presently, the structure and function of P2Y10 is under investigation. For example, U.S. Pat. No. 5,834,587 to Chan et al. discloses the identification of the human G-protein-coupled receptor called HLTEX11 and the cloning of the gene encoding the same. Human HLTEX11 is also known as P2Y10 and for clarity and consistency, throughout the present disclosure the term P2Y10 is used to describe this polypeptide. As noted, Chan et al. disclose a nucleic acid sequence encoding a human P2Y10 polypeptide, as well as an amino acid sequence of the same. However, Chan et al. do not disclose modulating T lymphocyte activity by employing an antibody directed against a P2Y10 polypeptide having one or more of the following properties: (a) the ability to activate a resting T lymphocyte; (b) the ability to induce surface expression of P2Y10 on a resting T lymphocyte; (c) the ability to stimulate P2Y10 mRNA expression in a resting T lymphocyte; and (d) the ability to inhibit proliferation of an activated T lymphocyte.
Thus, although a nucleic acid sequence encoding a human P2Y10 polypeptide, as well as an amino acid sequence of a human P2Y10 polypeptide, is known, until the present disclosure, a modulator of T lymphocyte function that interacts with P2Y10 and has different functions depending on the state of the T lymphocyte has not been described. Therefore, what is needed is a modulator of T lymphocyte function that interacts with a P2Y10 polypeptide, for example an anti-P2Y10 antibody. Such a T lymphocyte modulator could be employed as a therapeutic agent, as a component of a therapeutic agent, as a component of a diagnostic method or as a component of a diagnostic or therapeutic kit. As described more fully herein below, the present invention solves this and other problems.